JPH0220832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a pump in a hydraulic machine.

In hydraulic machines, the law of similarity holds true between the actual machine and a model that has the same geometric shape. Therefore, generally, model experiments are conducted in a laboratory, and the performance of the actual machine is predicted using the similarity law based on the results. Figure 1 shows the performance of a model pump of a general hydraulic machine with guide vanes.The horizontal and vertical axes are model test flow rate Q _n and model test head
H _n and model test efficiency η _n are determined. In this diagram,
1 is a model-specific characteristic curve showing the relationship between the model test head H _n and the model test flow rate Q n at the model test rotation speed _{N n} when the guide vane opening degree is fixed, and 2 is the model efficiency corresponding to this characteristic. Curve 3 is the envelope curve of the model head/flow characteristic curve 1, 4 is the envelope curve of the model efficiency curve 2, a and b are the points corresponding to the highest head of the actual machine and the lowest head of the actual machine, respectively, when the actual machine operating range is L, H _na and H _nb are point a and b respectively
The model head at the point, Q _na and Q _nb are each a
The model flow rate at point and point b is shown.

In pump operation of hydraulic machinery, generally,
It is operated along a model head/flow rate envelope curve 3 corresponding to an envelope curve 4 connecting the highest efficiency points of the efficiency curve.

The general conversion formula for determining actual machine performance from model performance based on the law of similarity is: H=(N/N _n・D/D _n ) ² H _n ……(1) Q=N/N _n (D/D _n ) ³ Q _n ...(2) P=gQH/η ...(3) η=η _n +Δη ...(4)

Here, N: Actual machine rotation speed N _n : Model test rotation speed D: Actual machine representative dimensions D _n : Model representative dimensions H: Actual machine head H _n : Model test head Q: Actual machine flow rate Q _n : Model test flow rate P: Actual machine input g: Acceleration of gravity η: Actual machine efficiency η _n : Model test efficiency Δ〓: Correction value between actual machine efficiency and model efficiency There is a constant value between the actual machine efficiency and model efficiency, which is determined according to the difference between the actual machine dimensions and the model dimensions. Since it is empirically known that there is a relationship, Δη is determined using this relationship.

Figure 2 shows the performance of an actual machine in steady operation of a pump of a hydraulic machine operated at a constant rotation speed according to the conventional technology. It was determined by determining the actual machine dimensions and using equations (1), (2), (3), and (4). In FIG. 2, the horizontal axis shows the head, and the vertical axis shows the efficiency, input, and flow rate, and curves 5, 6, and 7 show the efficiency, input, and flow rate, respectively.
The model test heads H _{na and} H _nb at the model test points a and b shown in Fig. 1 correspond to the actual machine heads H _A and H _B in Fig. 2, and the model test flow rates Q _na and Q _{nb in Fig. 2 correspond to the actual machine heads H A and H B} in Fig. 2. They correspond to the actual machine flow rates Q _A and Q _B , respectively. Furthermore, the actual machine input and efficiency are expressed as P _A , P _B and η _A η _B , respectively.

The capacity of the electric motor directly connected to the pump of the hydraulic machine or the pump-turbine is determined to exceed the maximum input value of the actual machine performance, but as is clear from Figure 2, in most operating head ranges,
This had the disadvantage that the motor had to be operated at less than its designed capacity.

The purpose of the present invention is to eliminate such drawbacks and provide a pump operation method for a hydraulic machine that can be operated with a constant input commensurate with the design capacity in all head regions, and based on the inherent model pump performance of the hydraulic machine. Using the law of similarity, find the relationship between the head, flow rate, and input at various rotational speeds of the actual machine, and use the obtained relationship to determine the maximum input value in at least a part of the operating head range or the maximum input value determined as the pre-planned equipment capacity. a preliminary step of determining the relationship between the head and the maximum input value and the rotational speed, and converting a head signal corresponding to the head determined from the water level condition into a rotational speed signal using the relationship obtained in the preliminary step. and a step of controlling the operation of the hydraulic machine at a constant maximum input over at least a portion of its operating range at the rotational speed determined in the step.

Even if the head changes depending on water level conditions, the system automatically selects a rotation speed that keeps the input constant and operates at a variable speed, which matches the design capacity of the motor in all actual pump operating ranges. Can be operated at maximum input. As a result, the electric motor can be used effectively, the amount of water pumped by the pump can be increased, and the pump operating time for obtaining the same amount of water can be shortened.

Examples will be described below.

FIG. 3 is a block diagram of a pump operating method according to an embodiment, in which 8 is a signal converter, 9 is a rotational speed controller, 10 is a generator motor, 11 is a pump turbine governor, and 12 is a pump turbine. ing. The signal converter 8 converts a head signal corresponding to the head H determined from the water level relationship into a rotational speed signal corresponding to the rotational speed at which the machine should be operated. It has a function of selecting a rotation speed N that satisfies the condition , and converts the head H into a rotation speed signal corresponding to a uniquely determined rotation speed. This rotational speed signal is transmitted to a rotational speed controller 9 consisting of a cycloconverter or the like. The rotation speed controller 9 changes the transmitted rotation speed signal to a frequency that uniquely corresponds to the rotation speed to be operated, and uses this frequency to control the generator motor 10.
frequency control is performed without disturbing the system frequency. On the other hand, based on this rotational speed signal, the opening degree of the guide vanes provided on the pump-turbine 12 is controlled via the pump-turbine speed governor 11 . By using such a pump operating method, it is possible to operate the pump with constant input in all head ranges.

FIG. 4 shows an example of a signal converter, which includes a signal converting element 14 that converts a head signal into a rotation angle of the cam 13;
It consists of a cam 13, which has a relationship between rotational speed and head that keeps the input constant on the cam curved surface, and a signal conversion element 15 that converts the rotational angle of the cam 13 into a rotational speed signal. In this signal converter, the head signal is converted into a rotational angle change amount by a signal conversion element 14 consisting of a potentiometer or the like. This amount of change in rotational angle is converted into an amount of change in the vertical direction of the cam curved surface, and converted into a rotational speed signal by a signal conversion element 15 made of a differential transformer or the like.

Next, the relationship between the rotational speed and the operating speed that maintains a constant input condition is determined as follows.

First, the flow rate Q and the input P in the case of various actual machine rotational speeds N are calculated using equations (1), (2), (3), and (4) from the model performance specific to the hydraulic machine.

Figure 5 shows the results when the rotational speed at which the actual machine performance shown in Figure 2 was obtained is taken as N. The horizontal axis is the head H, and the vertical axis is the input P and flow rate Q.
In either case, N increases as one goes up. The inputs P at the heads H _A and H _B are shown as P _A and P _B , respectively, and the flow rates Q are shown as Q _A and Q _B, respectively. Assuming that the input takes the maximum value P _B at the lowest head H _B , select the operating point that keeps P _B constant.
In other words, if the input curve is set to be P _C , the flow rate curve corresponding to the head H is expressed as Q _C ,
Q _C is the flow rate envelope curve when the input is constant, and Q _A ′ is the pump flow rate at the head H _A when the input is constant. Using this result, head H and rotational speed N
Figure 6 shows that these relationships are expressed by a uniquely defined envelope curve.

Therefore, if the pump operation method of this embodiment is used, it is possible to always operate the pump at the maximum input corresponding to the maximum capacity of the electric motor, and as is clear from Fig. 5, the pump operation at the maximum head H _A is possible. The flow rate can be increased up to Q _A Q _A ′. Also,
It is possible to obtain a pump pumping amount in the range surrounded by Q _A ′, Q _B , and Q _A ′, making it possible to increase the pumping amount per hour. As a result, equipment or equipment can be operated most effectively.

The same effect can be obtained even if the signal converter is an electrical signal converter such as a microprocessor that provides a rotational speed signal with a constant input head signal corresponding to the head H. In addition to the method shown in the block diagram in Fig. 3, it is also possible to
Any operating method that selects the rotation speed for steady operation of the actual machine under constant input conditions can be used in the same way.
A similar effect can be obtained.

As described above, the present invention makes it possible to provide a method for operating a pump of a hydraulic machine that can be operated with a constant input commensurate with the design capacity, and has great industrial effects.

[Brief explanation of drawings]

Figure 1 is a diagram showing the general model pump characteristics of a hydraulic machine with guide vanes, Figure 2 is a diagram showing the characteristics of a typical actual pump when operated at a constant rotation speed, and Figure 3 is FIG. 4 is a block diagram of an embodiment of the method of operating a pump for a hydraulic machine according to the present invention.
An explanatory diagram of the signal converter used in the operating method shown in Fig. 5. Fig. 5 is a diagram showing the change in general performance when the rotation speed is changed and the characteristics when the input condition is kept constant. Fig. 6 is a diagram showing the characteristics when the input condition is kept constant. FIG. 3 is a diagram showing the relationship between head and rotation speed when a constant input condition is maintained. 8...Signal converter, 9...Rotation speed controller, 1
0... Generator motor, 11... Pump water turbine governor,
12...Pump water wheel, 13...Cam, 14,15
...Signal conversion element.

Claims (1)

[Claims] 1 Based on the inherent model pump performance of the hydraulic machine, use the law of similarity to find the relationship between the head, flow rate, and input at various rotational speeds of the actual machine, and from the obtained relationship, calculate the maximum input value in at least a part of the operating head range, or A preliminary step in which a maximum input value determined as the planned equipment capacity is selected and the relationship between the head and the maximum input value and the rotational speed is obtained, and a head signal corresponding to the head determined from water level conditions is obtained in the preliminary step. a step of converting the obtained relationship into a rotational speed signal; and a step of controlling the operation of a hydraulic machine at a constant maximum input over at least a portion of its operating range at the rotational speed determined in the step. How to operate the machine pump.